Good first version... Rated 4 out of 5 stars
This Flickr Gallery Plus extension is a very nice first version. Flickr's photo set navigation always confused me a bit, mostly in its inability to give the user a clear overview of its current position within the set. This extension solves that nicely! The slideshow a nicely added touch.
One point of improvement I would like to suggest is reconsidering the inclusion of an icon in the status bar to enable or disable the functionality. I truly dislike extensions who needlessly put icons in my status bar (and even use the extension called Organize Statusbar to hide some of them).
Is there a possibility for you to include this toggle within the Flickr website itself, where it's relevant? This also improves its findability, as I had to read the author's document to figure out how this extension works exactly.